Expansion-bit.



J. W. CALDWELL.

EXPANSION .BIT.

uruouxou mum JUHE24,1908. nmnwzn mm. 2 1912.

1,066,707. Patented July 8, 1913.

[127 812 [or IKIaZ/M wml z W? UNITED STATES PATENT OFFICE. I

OHN WILLIAM CALDWELL, OF TQRONTO, ONTARIO, CANADA.

EXPANSION-BIT.

Specification of Letters Patent Patented J uly 8,1913.

Q-pglication filed lune 24, 1808, Serial No. 440,178. Renewed December 2, l9l2.' Serial No. 734,623.

To all whom it may come-m;

Be it known that I, Jons' lVnJaAirG-mn- .wsLL, a subject of the Kingot Great Britain, and resident of the city of Toronto, in the county of York, in the Province of Ontario, in the Dominion of Canada, haveinvented certain ne v and useful Improvements in Expansion-Bits, of which the followingis a specification. 1

The invention relates to improvements in expansion bits as dcscribedin the following specification and illustrated in the aecom-- panying drawings that-form part of the same.

The in\'enti .-n consists essentially in the novel coi istruction and arrangementof parts wherebyhn adjustable cutter is arrai'iged in the spiral body portion of a bit formed in cross section with 'iar'allel straight faces of greater width than half the .diiuneter of the bit, so as to form, in itsvariouspositions, a

continuation of the said spiral at one side of the central lcadlsicrcw.

The objects of the invention ere to devise an expansion bit which will cut yarious sizes" of holes cvcnlyand truc andcarry the chips clear of the-hole without choking, and to provide a bit of simple and durable construction which may he sharpened readily and easily and quickly adjusted. p

The present-invention relates particularly to the adaptation of the auger bit described in my co-pending application 440,177 to an expansion bit.

In the drawings Figure l is a perspective view of the bit broken intermediate of. its length, and showing a cross section. Fig. 2 is a detail of the cutting end. Fig. 3 is a detail of the cutting end showing the movable cutter extended. Fig. 4 is an end view of the bit. v

Referring to the drawings 1 is the spiral having the body 2 formed with parallel straight faces 3 connecting the side flanges 4 laterally projecting at the outer edges, thus forming a pair of spiral channels of considcrably greater width than half the diameter of the bit. The body 2 is thickened at the lower end 5 and sharpened on one side to a cutting edge 6 extending from the center to the outer edge, and on the otherside provided with a. dove-tail shaped channel 7 extending from side to side thereof in a perfectly straight line.

- 8 is a straight shallow channel formed above-the dove-tail channel 7 havingan inwardly beveled upperside 9.

10 an adjustable cutter having a dovccued with tile marks, or in any other suitable manner.

14 is a block having a beveled npperedge and fitting into the channel 8 and rigidly secured in place by a pair of screws 15; The under surface of the block M-is roughened .in a corresponding manner to the upper side of the cutter, andis held tightly against said the press-tire of'thc screws 15.

spiral form ot-bittoexpalnsion'bit s on aecuttcr to hold it in anadjusted position by count. ot the lack of'clearance-in the spiral portion; which would c'hoke atpd prevent the prop'crcleiiring of the cutter, at in the prescome by t 'e peculiar formation of the-spiral in which the chips have :to travel are much wider than the width of the chips cut, and the wide channels extend directly from the cutting edges, so that'the chips can not choke or wedge between the flange of the bit an the side wall of the hole being cut.

16 is a lead screw extending downwardly from the center of the body 2 having a double thread 17 formed with an undercut inner surface and terminating in a pair of chisel points-18. One of the threads 17 forms a formed in the outer side of the adjustable. cutter l0 and in the side of the bit adjacent to the stationary .cuttcr (3 respectively hai'ingthcside walls thereof tapered slightly from portion which is so'formed that the channels" 50 cnt invcn ion this difficulty is entirely overthe bottom, said slots being also arranged centrally in relation to the flattened faces 19 and 20 in the cutters 6 and 10 respectively.

21 and 22 are side cut-tors having tapered dovetail portions adapted to fit into the dove-tail slots 19 and 20 and to wedge tightly therein with the sharpened cutting portion 23 projecting below the lower end of the bit.

The cutters 20 and .21 are wedged tight-{y into place, and when worn out-may be easi removed and replaced by new cutters,thu s the wearing of the side cutters .will npt shorten the life of the bit as is the case'w tli various bits at presentin use. v

An expansion bit constructed as herein shown and described is very'eflicient in its operation, cutting the wood away for the complete diameter of the hole and completely through.

The expansion cutter is arranged in the same plane as the stationary cutter. It will thus be seen that the wholearea of the surface being cut is cut on the em. level, ..and therefore there will be no danger of any one portion of the bit breaking through the wood on nearing thecompletion of the hole in advance of the other portion, as is the case with bits at. present in use. This feature allows the lead screw to retain its hold in the wood until the outside'cutter completes its work,

and thus feeds the said cutter inwardly untilthe hole is completed.

One length of expansion cutter is shown, but it must be understood that longer cutters may be substituted, and very large holes cut by the one size bit.

The bit shown in, the drawings shows a shank to be fitted to the ordinary hand brace, but it must be understood that this form of bit may be used in wood working machines, and may also be adapted'for use as an auger in boring large holes, and it is only necessary to form the article with the-nfost desirable form of shank for the purposefoi which it is to be used. 1

What I claim as my invention is 1; In an expansion bit, a spiral body-portion havinga cross sectional shape showing parallel straight faces, said straight faces peripheral curve of said body po peering as extending laterally from said parallel straight faces at each end'and forming guiding shoulders for the chips in their travel along said channels and an adjustable cutter secured in the lower end of said spiral and forming a continuation thereof.

3. In an expansion bit, a spiral body por tion having a cross sectional shape showing parallel straight faces, said straight faces presenting channels of greater width than half the diameter of the bit, said body portion having a rigid horizontal cutter formed at one side thereof extending from thecenter outwardly, and an adjustable cutter secured in the opposite side of said body portion to said rigid cutter and forming a continuation of said spiral.

4. In a device of the classde scribed a l spiral body portion having flanged edges, said flangegadjacent to the lower end having vertical flattened faces; and tapered vertical dovetailed grooves centrally in relation to said flattened faces, and side spur cutters having tapered dove-tail portions adapted to'fit said tapereddove-tailed.

grooves and flattened inner faces adapted to arranged abut the flattened faces on said body portion and rounded outer sidesconforming to the cutting ends projecting beyond said spiral. .Signed at the city of Toronto, in the n and county of York, in the Province of Ontario,

in the Dominion of Canada this 16th day of June, 1908. JOHN WILLIAM CALDWELL. Witnesses:

H. DnNmsoN, 4 WM. C. Mum. 

